1. Field of the Invention
The present invention is related to an apparatus and method for controlling a recording light signal. More particularly, the present invention is related to an apparatus and method for controlling the recording light signal in accordance with changes in operational characteristics of the recording light signal.
2. Description of Related Art
Light sources used in optical recording and reproducing apparatuses, e.g., blu ray disc (BD), compact disc (CD), digital versatile disc (DVD), high definition (HD)-DVD, have operational characteristics that may change due to a number of factors, e.g., temperature, age and humidity. Only if the optical recording and reproducing apparatus has a stable light source can data on an optical disk be faithfully recorded and reproduced.
In addressing this problem, optimum power control (OPC) has been used. For OPC to be realized, disc manufacturers store suitable recording power values in lead in areas of recordable discs. An optical disc recording apparatus tests the suitable recording power values to obtain an optimum or target power when a disc is loaded in the optical disc recording apparatus.
FIG. 1 illustrates a block diagram of a conventional automatic light power controller (ALPC) 5. Here, the light source controlled by the ALPC 5 is illustrated as a laser diode (LD) 2 whose output is monitored by a detector 3. The ALPC 5 may include a reference voltage generator 51, a comparator 52, a target power operation circuit 53, an LD driver 54 and an LD output monitor.
The reference voltage generator 51 outputs a reference voltage Vr corresponding to the target power obtained by the OPC process. The LD output monitor 55 receives the output from the detector 3 and outputs a corresponding monitored voltage Vm. The comparator 52 compares the reference voltage Vr with the monitored voltage Vm and outputs the difference. The target power operation circuit 53 adds or subtracts the difference to or from the previous recording signal to compensate for the previous recording signal, and outputs the compensated signal as the write signal WS. The LD driver 54 converts the voltage values of the compensated recording signal into current values and drives the LD 2 with the compensated recording signal. Thus, the ALPC 5 automatically compensates for any changes in the output of the LD 2, and, thus, of the recording light signal or write pulse WP.
FIG. 2 illustrates waveforms used in the operation of the optical recording and reading apparatus. As shown in FIG. 2, the write signal WS includes an overdrive power, a recording power, a cooling power and a reading power. As shown in FIG. 2, the output of the optical detector 3 in response to the write signal WS is analog, and does not exactly follow the waveform of the write signal WS. As shown in FIG. 2, a sample pulse SP of the sample and hold signal of the LD output monitor 55 samples during stable record and read operations. Thus, the conventional ALPC 5 only compensates the recording and reading power, i.e., does not compensate the overdrive power and the cooling power. Even if the sampling frequency is increased, the conventional ALPC cannot obtain the exact value of the overdrive and cooling power. Thus, recording quality may be poor.